Modified Bitumen Roofing

What is Modified Bitumen?

Modified bitumen is a common type of membrane roofing made primarily from asphalt. However, it is modified using layers of fiberglass or polyester to add durability to the layers of a flat roofing system. It can be made to allow applications in both hot and cold temperatures.

Bitumen roofs have become one of the modern standards in roofing due to its exceptional durability easily allowing it to last for more than 20 years or more. During the installation process whether it’s been modified to be applied through (cold-applied adhesive, self-adhering sheets, or hot-mopped asphalt) any seams generally melt together to help eliminate leaks.

Common Types of Modified Bitumen

In the commercial roofing industry today, there are two primary types of modified bitumen that are commonly used. They are:

APP: Atactic Polypropylene is a thermoplastic polymer made for increased performance. This increases the bitumen’s ability to handle the elements such as increased flexibility in low temperatures, a much higher UV resistance, and increased resistance to flow at higher temperatures. These are generally installed by using a propane torch. The heat is used to soften the bottom of the bitumen sheets turning it into a molten adhesive. When installed this allows the seams to flow together making a waterproof bond.

SBS: Styrene-Butadiene-Styrene is another form of modified asphalt created by making a network of polymer within the bitumen sheets. This gives it characteristics very similar to rubber with much better resistance to aging and weathering. These SBS sheets are generally installed through hot mopping, torching, or even cold application adhesives. These sheets once applied will need some form of an ultraviolet protective coating as they are not made with granule or foil surfacing during manufacturing.